Pusher assemblies for use in microfeature device testing, systems with pusher assemblies, and methods for using such pusher assemblies

ABSTRACT

Pusher assemblies for use in microelectronic device testing systems and methods for using such pusher assemblies are disclosed herein. One particular embodiment of such a pusher assembly comprises a plate having a first side and a second side opposite the first side. An engagement assembly is removably coupled to the second side of the plate and positioned to contact a microfeature device being tested. The pusher assembly can include an urging member proximate the first side of the plate and configured to move the engagement assembly toward the device being tested. The pusher assembly can also include a heat transfer unit carried by the first side of the plate. In several embodiments, the pusher assembly can further include a plurality of pins carried by the engagement assembly such that the pins extend through the plate and engage the urging member to restrict axial movement of the urging member toward the device being tested.

TECHNICAL FIELD

The present invention is related to pusher assemblies for use inmicrofeature device testing, systems with pusher assemblies, and methodsfor using such pusher assemblies.

BACKGROUND

Conventional microelectronic devices are manufactured for specificperformance characteristics required for use in a wide range ofelectronic equipment. A microelectronic bare die, for example, includesan integrated circuit and a plurality of bond-pads and/or redistributionlayer (RDL) pads electrically coupled to the integrated circuit. Thebond-pads can be arranged in an array, and a plurality of solder ballscan be attached to corresponding bond-pads to construct a “ball-gridarray.” Conventional bare dies with ball-grid arrays generally havesolder balls arranged, for example, in 6×9, 6×10, 6×12, 6×15, 6×16,8×12, 8×14, or 8×16 patterns, but other patterns are also used. Manybare dies with different circuitry can have the same ball-grid array butdifferent outer profiles.

Bare dies are generally tested in a post-production batch process todetermine which dies are defective. In one conventional test process,bare dies are placed in corresponding test sockets of a test tray andelectrical signals are applied to the dies in a controlled environment.FIG. 1, for example, is a schematic side cross-sectional view of aportion of a conventional testing system 10 including a test bed 20carrying a bare die 30. The test bed 20 includes a test socket 22 havinglead-in surfaces 24 and side surfaces 26 that define a recess 28 forreceiving the die 30. A tester interface 40 including a plurality oftest contacts 42 is positioned below the test bed 20 with the testcontacts 42 positioned to contact corresponding solder balls 32 on thedie 30. A pusher assembly 50 (shown schematically) is positioned abovethe die 30 and configured receive a force from an actuator 60 and movethe die 30 toward the tester interface 40 (as shown by the arrows A) sothat the test contacts 42 can apply electrical signals to the die fortesting. Although only a single test socket 22, die 30, and pusherassembly 50 are shown in FIG. 1, it will be appreciated that the system10 can include a number of test sockets 22 and pusher assemblies 50 fortesting a number of dies either individually or in a batch process.

The pusher assembly 50 is configured to exert a desired force on the die30 so that the solder balls 32 contact corresponding test contacts 42with a desired contact force and without damaging the solder balls.Precise and repeatable positioning of each die 30 with respect to thetest contacts 42 is essential for accurate and efficient testing of thedies. Examples of conventional pusher assemblies include the M6541-,M6741-, and M6542-series pusher assemblies commercially available fromAdvantest Corporation of Tokyo, Japan.

One problem with conventional pusher assemblies, such as the pusherassembly 50, is that it is difficult to perform testing for runs of dieswith different profiles. In many conventional testing systems, forexample, the pusher assemblies are specifically configured to be usedthroughout a testing run for dies having the same outer profile and/orball grid array. However, to test dies with different profiles or ballgrid arrays using the same test bed requires reconfiguring the pusherassembly to accommodate the different outer profile and/or ball grid ofthe new dies to be tested. The pusher assembly is generally reconfiguredby manually removing all or a substantial portion of the pusher assemblyfrom the system and attaching a different pusher assembly specificallysized and configured for the outer profile of the new dies to be tested.In a typical large scale manufacturing process for microfeature devices(such as bare dies), reconfiguring the pusher assemblies to test dieshaving a different outer profile typically involves reconfiguring alarge number of pusher assemblies. This process is accordingly extremelylabor-intensive, time-consuming, and expensive because it not onlyrequires a large inventory of pusher assemblies having differentconfigurations and many hours of skilled labor, but it also results incostly downtime for the testing systems.

Another problem with testing systems including conventional pusherassemblies is that it can be difficult to keep the die and other systemcomponents at a desired temperature throughout the testing process. Thelack of a heat transfer device on conventional pusher assemblies cancreate a significant problem with overheating during testing. Further,the addition of such a heat transfer unit to many conventional pusherassemblies would interfere with the operation and placement of thepusher assembly within the testing system. Accordingly, there is a needfor an improved pusher assembly for use in microfeature device testingsystems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially schematic, side cross-sectional view of a portionof a system for testing microfeature devices in accordance with theprior art.

FIG. 2 is a partially schematic, exploded isometric view of a system fortesting microfeature devices in accordance with an embodiment of theinvention.

FIG. 3A is an exploded, isometric view of the pusher assembly of FIG. 2illustrating a number of the pusher assembly's components in a generallydisassembled state.

FIG. 3B is an isometric view of the pusher assembly of FIG. 3A afterassembling the various components.

FIG. 4 is an exploded, isometric view of a pusher assembly for use in asystem for testing microfeature devices in accordance with anotherembodiment of the invention.

DETAILED DESCRIPTION

A. Overview

The present invention is directed toward pusher assemblies for use inmicrofeature device testing, systems with such pusher assemblies, andmethods for using such pusher assemblies. One particular embodiment ofsuch a pusher assembly comprises a plate having a first side and asecond side opposite the first side. An engagement assembly is removablycoupled to the second side of the plate and positioned to contact amicrofeature device being tested. The pusher assembly includes an urgingmember proximate the first side of the plate and configured to move theengagement assembly toward the device being tested. The pusher assemblyalso includes a heat transfer unit carried by the first side of theplate. In several embodiments, the pusher assembly can further include aplurality of pins carried by the engagement assembly such that the pinsextend through the plate and engage the urging member to restrict axialmovement of the urging member toward the device being tested.

Another embodiment of a pusher assembly for use in a system for testingmicrofeature devices includes a plate having a first side, a second sideopposite the first side, and an aperture extending completely throughthe plate. The plate includes a first shaft and a second shaftprojecting from the first side of the plate. An engagement assembly isremovably coupled to the second side of the plate. The engagementassembly includes (a) a base portion in direct contact with at least aportion of the second side of the plate, and (b) an engagement elementprojecting from the base portion and positioned to contact amicrofeature device being tested. The pusher assembly also includes afirst urging member carried by the first shaft and a second urgingmember carried by the second shaft. The first and second urging membersare positioned to urge the engagement assembly toward the device beingtested. The pusher assembly further includes a plurality of pinsremovably carried by the base portion such that the pins extend throughthe plate and engage the corresponding first and second urging members.The pins have a predetermined length to restrict axial movement of thefirst and second urging members toward the device being tested. Thepusher assembly also includes a heat transfer unit carried by the firstside of the plate such that the heat transfer unit is in direct thermalcontact with the engagement assembly.

Still another embodiment of the invention is directed toward a systemfor testing microfeature devices. The system includes a test assemblyhaving a test tray insert and a device carrier carried by the test trayinsert. The device carrier is configured to receive a microfeaturedevice for testing. The system also includes a test contact assemblyhaving test contacts positioned to selectively contact correspondingconductive elements on the device being tested. The system furtherincludes a pusher assembly configured to move a device being tested froma first position in the device carrier in which the conductive elementsare out of contact with the corresponding test contacts to a secondposition in which at least a portion of the test contacts are engagedwith corresponding conductive elements. The pusher assembly includes aplate having a first side and a second side opposite the first side. Anengagement assembly is removably coupled to the second side of the plateand positioned to contact a microfeature device being tested. The pusherassembly also includes an urging member proximate the first side of theplate and configured to move the engagement assembly toward the devicebeing tested. The pusher assembly further includes a heat transfer unitcarried by the first side of the plate.

The term “microfeature device” is used throughout to includemicroelectronic devices, micromechanical devices, data storage elements,read/write components, and other articles of manufacture. For example,microfeature devices include SIMM, DRAM, flash-memory, ASICS,processors, imagers, flip chips, ball-grid array chips, and other typesof microelectronic devices or components. Many specific details ofcertain embodiments of the invention are set forth in the followingdescription and in FIGS. 2-4 to provide a thorough understanding ofthese embodiments. A person skilled in the art, however, will understandthat the invention may be practiced without several of these details oradditional details can be added to the invention. Well-known structuresand functions have not been shown or described in detail to avoidunnecessarily obscuring the description of the embodiments of theinvention. Where the context permits, singular or plural terms may alsoinclude the plural or singular term, respectively. Moreover, unless theword “or” is expressly limited to mean only a single item exclusive fromthe other items in reference to a list of two or more items, then theuse of “or” in such a list is to be interpreted as including (a) anysingle item in the list, (b) all of the items in the list, or (c) anycombination of the items in the list. Additionally, the term“comprising” is used throughout to mean including at least the recitedfeature(s) such that any greater number of the same feature and/oradditional types of features are not precluded.

B. Embodiments of Systems for Testing Microfeature Devices

FIG. 2 is a partially schematic, exploded isometric view of a system 200for testing a microfeature device 202 in accordance with an embodimentof the invention. More specifically, the system 200 includes a pusherassembly 240 configured to move the device 202 into contact with a testassembly 208 including an array of test contacts for testing of thedevice 202 to ensure and verify that the device 202 functions accordingto specification. The individual microfeature device 202 can be asingulated bare die or another device having a substrate 204 and aplurality of conductive elements 206 (e.g., solder balls) projectingfrom the substrate 204. Although only a single microfeature device 202,test assembly 208, and pusher assembly 240 are shown in the illustratedembodiment, it will be appreciated that the system 200 can include anumber of test assemblies 208 and pusher assemblies 240 to test a numberof devices 202 either individually or in a batch process.

The test assembly 208 includes a test bed 210 having a test contactassembly 212 with a plurality of test contacts 214 arranged in an arraycorresponding at least in part to the array of conductive elements 206on the device 202. The contact assembly 212 is operably coupled to acontroller 216 that sends/receives signals from the device 202 duringtesting.

The test assembly 208 also includes (a) a socket guide 220 removablyreceived by the test bed 210 and (b) a test tray insert 230 carried bythe socket guide 220. The socket guide 220 includes an aperture 222aligned with the contact assembly 212 and a plurality of alignment pins224 (two are shown in the illustrated embodiment) positioned to receivecorresponding alignment apertures 232 in the test tray insert 230. Thealignment pins 224 and alignment apertures 232 accurately position thesocket guide 220 and corresponding test tray insert 230 with respect tothe contact assembly 212. As discussed in detail below, the alignmentapertures 232 also receive alignment portions of the pusher assembly 240to further align the components of the system 200 with respect to thecontact assembly 212. The test tray insert 230 further includes a devicecarrier 234 configured to receive the device 202. The device carrier 234includes an aperture 236 positioned to receive the conductive elements206 on the device 202.

The pusher assembly 240 includes a pusher housing 242, an engagementassembly 250, and a heat transfer unit 290. The pusher housing 242includes pusher alignment features 244 positioned to engagecorresponding alignment apertures 232 of the test tray insert 230 toaccurately align the pusher assembly 240 with respect to the contactassembly 212 and ensure that the device 202 is positioned to contact thedesired test contacts 214. The pusher housing 242 further includes aplurality of stand-offs 245 configured to engage corresponding referencesurfaces 226 on the socket guide 220 to position the pusher assembly 240at a desired location with respect to the test bed 210.

In operation, an actuator 209 provides a force to the pusher assembly240 such that the engagement assembly 250 engages or otherwise contactsthe device 202 to move the device from a first position in the devicecarrier 234 with the device's conductive elements 206 generally out ofcontact with the test contacts 214 to a second position with at least aportion of the conductive elements 206 in contact with correspondingtest contacts 214. As described in greater detail below with referenceto FIGS. 3A-4, aspects of the invention are directed to pusherassemblies that support such an installation (as well as others), andthat include (a) the ability to adjust the applied force based on theconfiguration of the device under test, and (b) a heat transfermechanism.

C. Embodiments of Pusher Assemblies for Use in Microfeature DeviceTesting Systems and Methods for Using Such Pusher Assemblies

FIGS. 3A and 3B are isometric views of the pusher assembly 240 of FIG. 2without the pusher housing to illustrate various aspects of the pusherassembly in greater detail. More specifically, FIG. 3A is an exploded,isometric view of the pusher assembly 240 illustrating a number of thepusher assembly's components in a disassembled state, and FIG. 3B is anisometric view of the pusher assembly 240 after assembling the variouscomponents.

Referring to FIG. 3A, the engagement assembly 250 includes a bodyportion 252 positioned to be releasably attached to a pusher baseassembly 270 with one or more suitable fasteners 253 (two are shown inthe illustrated embodiment). The engagement assembly 250 is a modularcomponent that can interchanged with a number of other engagementassemblies having different configurations based at least in part on theconfiguration and/or dimension of the device being tested (e.g., outerprofile of device, arrangement of electrical couplers on device, numberof electrical couplers, type of electrical couplers on device, etc.).The body portion 252 includes a projection 254 sized to be receivedwithin a corresponding aperture or opening in the base assembly 270 andattachment portions 256 positioned to engage corresponding attachmentportions of the base assembly 270. A plurality of pins (e.g., loadingpins) or stand-offs 258 project from the attachment portions 256 towardthe base assembly 270. The pins 258 are interchangeable components thatcan be releasably attached to the engagement assembly 250 by pressing orotherwise pushing the individual pins into corresponding pin apertures259 in the body portion 252. The individual pins 258 have a height Hthat is based (at least in part) on the specific configuration of thedevice being tested and the desired force to be applied to the device bythe pusher assembly 240. As described in greater detail below, the pins258 are positioned to engage one or more urging members carried by thebase assembly 270 and restrict the axial movement of the urging memberstoward the device being tested, thereby controlling and/or limiting thecontact force the pusher assembly 240 exerts upon the device. Althoughsix pins 258 are shown in the illustrated embodiment, the engagementassembly 250 can include a different number of pins and/or the pins canhave a different arrangement.

The engagement assembly 250 also includes an engagement element 260projecting from the body portion 252. The engagement element 260includes a contact surface 262 configured to directly contact the devicebeing tested and move the device into contact with the correspondingtest contacts. The contact surface 262 accordingly is specificallyshaped and dimensioned for contact with a device having a certain outerprofile and/or planform shape. As explained in more detail below, theengagement element 260 can be quickly removed from the base assembly270. Another engagement assembly with a different engagement elementconfigured to contact a different device can be quickly interchangedwith the engagement assembly 250. This is expected to simplifyreconfiguring the system to test different devices and reduced theinventory of complete pusher assemblies 240 at a manufacturer.

Referring to both FIGS. 3A and 3B, the illustrated pusher base assembly270 is configured to releasably carry the engagement assembly 250 andthe heat transfer unit 290. The base assembly 270 can include athermally conductive plate 272 (i.e., a pusher body assembly) having afirst side 273 and a second side 274 opposite the first side 273. Theplate 272 includes an aperture 276 configured to receive at least aportion of the engagement assembly 250 (e.g., the projection 254) andone or more attachment portions 277 configured to receive suitablefasteners (not shown) to releasably attach the base assembly 270 to thepusher assembly housing 242 (FIG. 2) and/or the heat transfer unit 290.As best seen in FIG. 3B, the engagement assembly 250 is accordingly indirect thermal contact with the heat transfer unit 290. This featureprovides good heat transfer from the device being tested to the heattransfer unit 290.

The plate 272 also includes two or more shafts 278 (two are shown in theillustrated embodiment) projecting away from the first side 273 of theplate 272. One or more urging members or forcing elements 280 (two areshown in the illustrated embodiment) are carried by the shafts 278 andpositioned to axially move along the corresponding shafts 278 as a forceis applied to the pusher assembly 240. In the illustrated embodiment,the urging members 280 are springs having a known spring rate or force.The spring rate can correspond at least in part to the desired contactforce to be applied to the device being tested.

The individual shafts 278 also carry a load ring 282 and a collar 284.The load rings 282 are positioned between the first side 273 of theplate 272 and the corresponding springs 280. As described in greaterdetail below, the load rings 282 are configured to engage the pins 258and act as a stop for the springs 280 as the springs are compressed. Thecollars 284 are positioned at a distal end of the shafts 278 to keep thesprings 280 in place on the shafts 278 and provide a surface againstwhich the actuator 209 (FIG. 2) acts. The collars 284 can slide alongthe shafts 278 and are retained on the shafts 278 with a fastener 285.

As best seen in FIG. 3B, the individual pins 258 project through theplate 272 and contact or otherwise engage the corresponding load rings282 to position the load rings at a desired position proximate to a baseportion of the shafts 278. The height H of the pins 258 is generallyselected to pre-load the springs 280 in the range of the spring constantof the spring. In operation, the actuator 209 (FIG. 2) drives thecollars 284 against the springs 280. The springs 280 transmit the forcefrom the actuator 209 to the load rings 282 at the spring constant ofthe springs 280. As such, the springs 280 are compressed toward the loadrings 282 a specific axial length L along the shafts 278 based on theforce applied and the spring constant of the individual springs 280. Bycoordinating the spring rate of the springs 280 with the configuration(i.e., the height H) of the pins 258, the pusher assembly 240 canprecisely control the contact force exerted upon a device being tested.

One feature of the pusher assembly 240 described above with reference toFIGS. 2-3B is that the engagement assembly 250 is a modular componentthat can be removed from the pusher assembly 240 to (a) interchange thepins 258 with pins having a different configuration, and/or (b) replacethe entire engagement assembly 250 with an engagement assembly having adifferent configuration. One advantage of this feature is that replacingonly the engagement assembly 250 portion of the pusher assembly 240 is arelatively quick and easy process compared to the conventional systemsdescribed above where all or a substantial portion of each pusherassembly within the testing system had to be replaced before testing arun of dies having a different configuration.

Another advantage of this feature is that the cost of keeping aninventory of engagement assemblies having different configurations issignificantly less than the cost of keeping an inventory of entirepusher assemblies. The testing system 200 including the pusher assembly240, for example, provides about an 80% reduction in tooling cost ascompared with testing systems using conventional pusher assemblies wherea large number of different pusher assemblies must be kept on hand fortesting devices having different configurations.

Another feature of the pusher assembly 240 described above withreference to FIGS. 2-3B is that the engagement assembly 250 is in directthermal contact with the heat transfer unit 290. One advantage of thisfeature is that heat generated during testing can be withdrawn from thedevice being tested to keep the device and other system components at adesired temperature throughout the testing process. Another advantage ofthis feature is that the position of the heat transfer unit 290 on thepusher assembly 240 does not interfere or otherwise conflict with theplacement or movement of the pusher assembly within the testing systemand/or the operation of the force adjustment mechanism of the pusherassembly.

D. Additional Embodiments of Pusher Assemblies

FIG. 4 is an exploded, isometric view of a pusher assembly 440 inaccordance with another embodiment of the invention. The pusher assembly440 can be used with the system 200 of FIG. 2, or another suitablemicrofeature device testing system. The pusher assembly 240 can begenerally similar to the pusher assembly 240 described above withrespect to FIGS. 2-3B. Accordingly, like reference numbers refer to likecomponents in FIGS. 2-3B and FIG. 4.

The pusher assembly 440 differs from the pusher assembly 240 describedabove in that the pusher assembly 440 includes an urging member having adifferent configuration than the urging members 280 of the pusherassembly 240. More specifically, the pusher assembly 440 includes apusher base assembly 470 with the plate 272 and the shafts 278projecting from the first side 273 of the plate 272. The pusher assembly440, however, includes only a single urging member 480 (e.g., a springor other suitable forcing element) carried by the pusher base assembly470 rather than the two urging members 280 described above with respectto FIGS. 3A and 3B. The urging member 480 is sized to fit around atleast a portion of each shaft 278 and the heat transfer unit 290.

The urging member 480 can function in much the same way as the urgingmembers 280 of the pusher assembly 240 described above with respect toFIGS. 2-3B. For example, the urging member 480 is configured to axiallymove along the shafts 278 as a force is applied to the pusher assembly440. The axial movement of the urging member 480 is restricted orotherwise limited by the pins 258 projecting upwardly through the plate272 from the engagement assembly 250. The urging member 480 can have apredetermined spring rate or force based at least in part on theconfiguration of the device being tested and/or the configuration of theengagement assembly 250.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from theinvention. Aspects of the invention described in the context ofparticular embodiments may be combined or eliminated in otherembodiments. Further, while advantages associated with certainembodiments of the invention have been described in the context of thoseembodiments, other embodiments may also exhibit such advantages, and notall embodiments need necessarily exhibit such advantages to fall withinthe scope of the invention. Accordingly, the invention is not limitedexcept as by the appended claims.

1. A pusher assembly for use in a system for testing microfeaturedevices, the pusher assembly comprising: a plate having a first side anda second side opposite the first side; an engagement assembly removablycoupled to the second side of the plate and positioned to contact amicrofeature device being tested; an urging member proximate the firstside of the plate, the urging member being configured to move theengagement assembly toward the device being tested; and a heat transferunit carried by the first side of the plate.
 2. The pusher assembly ofclaim 1, further comprising a plurality of pins carried by theengagement assembly such that the pins extend through the plate andengage the urging member to restrict axial movement of the urging membertoward the device being tested.
 3. The pusher assembly of claim 2wherein: the plate includes a first shaft and a second shaft projectingfrom the first side of the plate; the urging member proximate the firstside of the plate includes a first spring carried by the first shaft andthe pusher assembly further includes a second spring carried by thesecond shaft; and the heat transfer unit is between the first shaft andthe second shaft and in direct thermal contact with the engagementassembly.
 4. The pusher assembly of claim 3 wherein: the pusher assemblyfurther includes (a) a first load ring carried by the first shaftbetween the first side of the plate and the first spring, and (b) asecond load ring carried by the second shaft between the first side ofthe plate and the second spring; and the pins contact the first andsecond load rings to restrict axial movement of the first and secondsprings along the first and second shafts, respectively, toward thedevice being tested.
 5. The pusher assembly of claim 2 wherein the pinsare interchangeable components removably carried by the engagementassembly.
 6. The pusher assembly of claim 2 wherein the pins have apredetermined length corresponding at least in part to the force of theurging member and/or an outer profile of the device being tested.
 7. Thepusher assembly of claim 1 wherein the urging member includes a springhaving a known spring constant such that the spring is configured toapply a predetermined force to the engagement assembly.
 8. The pusherassembly of claim 1 wherein the plate is a thermally conductive plate.9. The pusher assembly of claim 1 wherein the heat transfer unit is indirect thermal contact with the engagement assembly.
 10. The pusherassembly of claim 1 wherein the engagement assembly includes (a) a baseportion in direct contact with at least a portion of the second side ofthe plate, and (b) an engagement element projecting away from the baseportion and positioned to engage the device being tested.
 11. The pusherassembly of claim 10 wherein: the plate includes an aperture extendingcompletely through the plate; and the base portion of the engagementassembly further includes a projection extending through at least aportion of the aperture and in contact with the heat transfer unit. 12.The pusher assembly of claim 1 wherein the engagement assembly includesa contact surface positioned to directly contact the device beingtested, the contact surface having a predetermined configuration basedat least in part on a configuration of the device being tested.
 13. Thepusher assembly of claim 12 wherein the contact surface includes apredetermined shape based at least in part on an outer profile of thedevice being tested.
 14. The pusher assembly of claim 12 wherein thecontact surface includes a predetermined planform shape based at leastin part on a planform shape of the device being tested.
 15. The pusherassembly of claim 1 wherein the engagement assembly is a modular,interchangeable component.
 16. The pusher assembly of claim 1, furthercomprising an actuator positioned to provide a known force to the urgingmember to move the engagement assembly toward the device being tested.17. A pusher assembly for use in a system for testing microfeaturedevices, the pusher assembly comprising: a plate having a first side, asecond side opposite the first side, an aperture extending completelythrough the plate, and a first shaft and a second shaft projecting fromthe first side; an engagement assembly removably coupled to the secondside of the plate, the engagement assembly including (a) a base portionin direct contact with at least a portion of the second side of theplate, and (b) an engagement element projecting from the base portionand positioned to contact a microfeature device being tested; a firsturging member carried by the first shaft and a second urging membercarried by the second shaft, the first and second urging members beingpositioned to move the engagement assembly toward the device beingtested; a plurality of pins removably carried by the base portion suchthat the pins extend through the plate and engage the correspondingfirst and second urging members, the pins being a predetermined lengthto restrict axial movement of the first and second urging members towardthe device being tested; and a heat transfer unit carried by the firstside of the plate.
 18. The pusher assembly of claim 17 wherein the plateis a thermally conductive plate.
 19. The pusher assembly of claim 17wherein the heat transfer unit is in direct thermal contact with theengagement assembly.
 20. The pusher assembly of claim 17 wherein thebase portion of the engagement assembly includes a projection extendingthrough at least a portion of the aperture in the plate and in contactwith the heat transfer unit.
 21. The pusher assembly of claim 17wherein: the pusher assembly further includes (a) a first load ringcarried by the first shaft between the first side of the plate and thefirst urging member, and (b) a second load ring carried by the secondshaft between the first side of the plate and the second urging member;and the pins contact the first and second load rings to restrict axialmovement of the first and second urging members along the first andsecond shafts, respectively, toward the device being tested.
 22. Thepusher assembly of claim 17 wherein the pins are interchangeablecomponents removably carried by the base portion of the engagementassembly.
 23. The pusher assembly of claim 17 wherein the predeterminedlength of the pins corresponds at least in part to the force of thefirst and second urging members and/or an outer profile of the devicebeing tested.
 24. The pusher assembly of claim 17 wherein the first andsecond urging members include a first spring having a predeterminedspring constant and a second spring having a predetermined springconstant such that the individual first and second springs areconfigured to apply a predetermined force to the engagement assembly.25. The pusher assembly of claim 17 wherein the engagement elementincludes a contact surface positioned to directly contact the devicebeing tested, the contact surface having a predetermined configurationbased at least in part on a configuration of the device being tested.26. The pusher assembly of claim 25 wherein the contact surface includesa predetermined shape based at least in part on an outer profile of thedevice being tested.
 27. The pusher assembly of claim 25 wherein thecontact surface includes a predetermined planform shape based at leastin part on a planform shape of the device being tested.
 28. The pusherassembly of claim 17 wherein the engagement assembly is a modular,interchangeable component.
 29. A pusher assembly for use in a system fortesting microfeature devices, the pusher assembly comprising: supportmeans having a first side and a second side opposite the first side;engagement means removably coupled to the second side of the supportmeans and positioned for engaging a microfeature device being tested;urging means proximate the first side of the support means andpositioned for moving the engagement means toward the device beingtested; force adjustment means carried by the engagement means andpositioned for restricting the axial movement of the urging means towardthe device being tested; and heat transfer means carried by the firstside of the support means.
 30. The pusher assembly of claim 29 whereinthe support means includes a thermally conductive plate.
 31. The pusherassembly of claim 29 wherein the engagement means includes a contactsurface positioned to directly contact the device being tested, thecontact surface having a predetermined configuration based at least inpart on a configuration of the device being tested.
 32. The pusherassembly of claim 29 wherein the heat transfer means is in directthermal contact with the engagement means.
 33. A system for testingmicrofeature devices, the system comprising: a pusher assemblyincluding— a plate having a first side and a second side opposite thefirst side; an urging member proximate the first side of the plate, theurging member being configured to move the plate toward the devicesbeing tested; and a heat transfer unit carried by the first side of theplate; and an inventory of engagement assemblies configured to beremovably coupled to the second side of the plate and positioned tocontact each microfeature device being tested, the inventory including(a) a first engagement assembly having a first configuration based atleast in part on a configuration of a first microfeature device beingtested, and (b) a second engagement assembly having a secondconfiguration based at least in part on a configuration of a secondmicrofeature device being tested.
 34. A system for testing amicrofeature device including a substrate and an array of conductiveelements on the substrate, the system comprising: a test assemblyincluding a test tray insert and a device carrier carried by the testtray insert, the device carrier being configured to receive a device fortesting; a test contact assembly having test contacts, the individualtest contacts being positioned to selectively contact correspondingconductive elements on the device being tested; and a pusher assemblyconfigured to move a device being tested from a first position in thedevice carrier in which the conductive elements are out of contact withthe corresponding test contacts and a second position in which at leasta portion of the test contacts are engaged with corresponding conductiveelements, the pusher assembly including— a plate having a first side anda second side opposite the first side; an engagement assembly removablycoupled to the second side of the plate and positioned to contact thedevice being tested; an urging member proximate the first side of theplate, the urging member being configured to move the engagementassembly toward the device; and a heat transfer unit carried by thefirst side of the plate.
 35. The system of claim 34 wherein the pusherassembly further comprises a plurality of pins carried by the engagementassembly such that the pins extend through the plate and engage theurging member to restrict axial movement of the urging member toward thedevice.
 36. The system of claim 35 wherein the pusher assembly includesa first shaft and a second shaft projecting from the first side of theplate, and wherein: the urging member includes a first spring carried bythe first shaft and a second spring carried by the second shaft; and theheat transfer unit is between the first shaft and the second shaft andin direct thermal contact with the engagement assembly.
 37. The systemof claim 35 wherein the pins are interchangeable components removablycarried by the engagement assembly.
 38. The system of claim 35 whereinthe pins have a predetermined length corresponding at least in part tothe force of the urging member and/or an outer profile of the devicebeing tested.
 39. The system of claim 35 wherein the urging memberincludes a spring having a known spring constant such that the spring isconfigured to apply a predetermined force to the engagement assembly.40. The system of claim 34 wherein the plate is a thermally conductiveplate.
 41. The system of claim 34 wherein the heat transfer unit is indirect thermal contact with the engagement assembly.
 42. The system ofclaim 34 wherein the individual engagement assembly includes a contactsurface positioned to directly contact the device being tested, thecontact surface having a predetermined configuration based at least inpart on a configuration of the device being tested.
 43. The system ofclaim 34 wherein the engagement assembly is a modular, interchangeablecomponent.
 44. The system of claim 34, further comprising themicrofeature device.
 45. A method for testing microfeature deviceshaving a substrate and a plurality of conductive elements on thesubstrate, the method comprising: positioning the device within a devicecarrier such that the conductive elements on the device are out ofcontact with corresponding test contacts of a test contact assembly;moving the conductive elements into contact with corresponding testcontacts for testing with a pusher assembly, the pusher assemblyincluding an interchangeable engagement assembly configured to contactthe device with a desired force such that the conductive elements engagethe test contacts with a desired contact force; and removing heat fromthe device during testing with a heat transfer unit carried by thepusher assembly.
 46. The method of claim 45 wherein: the pusher assemblyincludes a plate having a first side, a second side opposite the firstside, an urging member proximate the first side, and the engagementassembly releasably coupled to the second side; and moving theconductive elements into contact with corresponding test contacts fortesting with a pusher assembly includes applying a first force to theurging member such that the urging member moves the engagement assemblyto contact the device with a second, predetermined force such that theconductive elements engage the test contacts with the desired contactforce.
 47. The method of claim 45 wherein: the pusher assembly includesa plate having a first side, a second side opposite the first side, afirst spring and a second spring proximate the first side, and theengagement assembly releasably coupled to the second side; and movingthe conductive elements into contact with corresponding test contactsfor testing with a pusher assembly includes applying a first force tothe first and second springs such that the first and second springs movethe engagement assembly to contact with the device with a second,predetermined force such that the conductive elements engage the testcontacts with the desired contact force.
 48. The method of claim 45wherein removing heat from the device with a heat transfer unit includesremoving heat from the device with a heat transfer unit in directthermal contact with the engagement assembly.
 49. The method of claim 45wherein the device is a first device and the engagement assembly is afirst engagement assembly, and wherein the method further comprises:removably attaching a second engagement assembly to the pusher assemblyin place of the first engagement assembly, the second engagementassembly having a configuration based at least in part on aconfiguration of a second device to be tested.
 50. The method of claim45 wherein the device is a first device with first conductive elementsand the engagement assembly is a first engagement assembly, and whereinthe method further comprises: positioning a second device within thedevice carrier, the second device including second conductive elementsout of contact with the corresponding test contacts; removably attachinga second engagement assembly to the pusher assembly in place of thefirst engagement assembly, the second engagement assembly having aconfiguration based at least in part on a configuration of the seconddevice; moving the second conductive elements into contact withcorresponding test contacts using the second engagement assembly suchthat the second conductive elements engage the test contacts with asecond desired contact force; and removing heat from the second devicewith the heat transfer unit.
 51. A method for manufacturing a pusherassembly for use in microfeature device testing systems, the methodcomprising: positioning one or more urging members on a first shaftprojecting from a first side of a plate and a second shaft projectingfrom the first side of the plate, the one or more urging members beingpositioned to move the plate toward a device being tested; removablyattaching an engagement assembly to the second side of the plate, theengagement assembly including a plurality of pins removably carried bythe engagement assembly extending through the plate and engaging the oneor more urging members to provide a stop that restricts axial movementof the one or more urging members toward the device being tested; andattaching a heat transfer unit to the first side of the plate.
 52. Themethod of claim 51 wherein positioning one or more urging members on afirst shaft projecting from a first side of a plate and a second shaftprojecting from the first side of the plate includes positioning a firsturging member on the first shaft and a second urging member on thesecond shaft, the first and second urging members having a predeterminedforce.
 53. The method of claim 51 wherein positioning one or more urgingmembers on a first shaft projecting from a first side of a plate and asecond shaft projecting from the first side of the plate includespositioning a first spring member on the first shaft and a second springmember on the second shaft, the first and second springs having apredetermined spring constant.
 54. The method of claim 51, furthercomprising providing a first urging member having a first known forceand a second urging member having a second known force, the first andsecond forces being based at least in part on the configuration of thedevice being tested.
 55. The method of claim 51, further comprisingproviding a thermally-conductive plate.
 56. The method of claim 51,further comprising selecting a plurality of pins having a predeterminedheight based at least in part on the configuration of the device beingtested.
 57. The method of claim 51, further comprising: placing a firstload ring on the first shaft between the first side of the plate and afirst urging member; placing a second load ring on the second shaftbetween the first side of the plate and a second urging member; andengaging the first and second load rings with corresponding pins suchthat the first and second load rings provide a stop that restricts axialmovement of the first and second urging members toward the device beingtested.
 58. The method of claim 51 wherein attaching a heat transferunit to the first side of the plate includes attaching the heat transferunit to the first side between the first shaft and the second shaft. 59.The method of claim 51 wherein removably attaching an engagementassembly to the second side of the plate includes positioning theengagement assembly in direct thermal contact with the heat transferunit.